THE PROBLEM OF INBREEDING 123 



The calculation is carried out in accordance with 

 the same principles as have been illustrated in the 

 previous cases. We have, from Pedigree Table III, 



and 



Zo = 100 (2-2) = 0> 



z = 100 (4-4) = 

 4 



since in generations 1 and 2 there are two and 

 four different ancestors respectively. 



Z 2 = ™°^> = 25, 

 o 



since in generation 3 the two individuals g and h 

 each appear twice, and by our rule any ancestor 

 is only counted once. 



Z 3 = 10 ° ( 16 ~ 8 > = 50, 

 16 



since in generation 4 the individuals m and n 

 appear four times and are only counted as different 

 ancestors once each, and individuals o and p each 

 appear twice. 



The data of Table 3 are given graphically in 

 Fig. 1, together with the curve for brother X 

 sister and parent x offspring. 



From the table and figure it is seen that with 

 continued inbreeding according to any one of these 

 four types the coefficient approaches the value 



